It is not always practical to produce a perfect prediction. It may not be desirable in some cases. However, it is practical to monitor performance. Such monitoring usually includes a combination of periodic inspections and continuous monitoring. This information is then compared with predictions or with certain limits to assess the approach to failure.
Results from monitoring are then fed back to operators and designers to determine whether modifications are necessary.
Lifetime Prediction, Roger W. Staehle, Adjunct Professor, Department of Chemical Engineering and Materials Science, University of Minnesota, Staehle Consulting Co.